Water heating is a thermodynamic process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating.
Water can be heated in vessels known as water heaters, tanks, kettles, cauldrons, pots, or coppers. A metal vessel that heats a batch of water does not produce a continual supply of heated water at a preset temperature. The water temperature varies based on the consumption rate, becoming cooler over time and as flow increases, and the vessel is depleted.